Old Parts


These are Galena holders. They hold the Galena.

The Galena crystal is probably the earliest popular semiconductor. They were used as detectors in early crystal sets. Other detectors have been used, but the Galena is the most sensitive. The only drawback is that the crystal had to be adjusted to find a sensitive spot. This was done by physically moving the contact wire (called the cat's whisker) until a good signal was heard. Someone had already taken the Galenas out of these holders.

Another popular, but less efficient detector was the razor blade / pencil type. My first exposure to this one was about 1955 when dad found the instructions in a Superman comic. The detector was made by fastening a Gillette Blue Blade to a board, then fastening a small length of graphite from a pencil to a safety pin. The pin acted as a spring, and the detector was adjusted by moving the graphite along the surface of the bluing, which created a rectifier.


This antenna tuner was used to modify the apparent electrical length of an antenna.

This is an AC magneto which generated the ringing signal in an old crank telephone.

It puts out about 95V at about 30 cycles (they didn't have Hertz back then) if you want to crank it hard enough. Enough power to run a small radio.


Here's an old crank telephone, or what's left of it.

Another early semiconductor is the selenuim rectifier. This was a real boon for designers who wanted to get away from rectifier tubes. The seleniums worked good, except that they had a high internal resistance, and when they went bad, they released selenium gas. I've whiffed my share of the stuff over the years. Today's silicon diodes can far outperform a selenium, and they take up less space than the mounting nut.

Mallory came up with this quick solution for the problem of finding odd value resistors. The Yardohm resistor stock was a fiberglass twine, wound with resistance wire. For any resistance you need, just cut off the length according to the chart, and crimp the leads in place.

I never used one, they're just a curiosity.

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